I've done a bit of striking and grappling. It seems like grappling is more strategic to me, although there is strategy in striking too. Its just that striking seems to have more focus on reflex, and there are fewer positions to remember and learn.

In grappling there is no end to the positions you can find yourself in, and the complexity is so deep you can study it for years and still learn new positions or attacks. This is why bjj is often compared to chess.

I really don't think you can say grappling is more complex than striking, there are endless combos, moves and reactions in Muay Thai for any situation or at least as many as in grappling BJJ/wrestling

I started in a striking-based martial art and at the time my mindset was all about stand-fighting. A few years later I found grappling, immediatly fell head over heels and I never went back to striking. I would definitly say my mindset has completely done a 180 towards grappling.

Unrelated, over the years I've seen many people come and go with respect to training. This was observed with those who were primarily grapplers or primarily kickboxers or a TMAer or some mix, whatever. With that observation and now that you bring up this concept of 'mindset', perhaps the mindset doesn't dictate what you train but rather it dictates whether you train in the first place, everyday, week after week, year after year.
An interesting topic to think about nonetheless; glad to see YMAS isnt't completly full of hijinks.